1. Field of Invention
This invention relates to power transformers. Specifically, the present invention relates to dual line balun transformers used to impedance match a receiver or a transmitter to an accompanying antenna to maximize power transfer.
2. Description of the Related Art
High power transmitters and receivers are used in a variety of demanding applications ranging from communications systems to radar systems. These applications often demand optimum power transfer between the associated transmitters or receivers and accompanying antennas.
Optimum power transfer is particularly important in systems employing high power transmitters over a wide range of bandwidths. In such systems, inefficient power transfer between the transmitters and associated antennas can result in wasted, reflected, and absorbed energy that can contribute to system electrical interference and undesirable heating of associated electronics.
Maximizing the power transfer from the antenna to the transmitter requires impedance matching the transmitter to the antenna.
To accommodate high bandwidth, i.e., wideband transmissions, coaxial baluns are often employed. Coaxial baluns typically include one or more high characteristic impedance coaxial cables to facilitate impedance matching of the transmitter to the accompanying antenna. However, high impedance coaxial cables require thin center conductors, which limits their power handling capability. The high resistivity of the thin center conductors results in excessive heating when employed in moderately high power applications. The excessive heating may result in the melting of electrical components.
Alternatively, conventional windings-based power transformers are often employed to impedance match a transmitter to an accompanying antenna. The transformers typically include a plurality of inductors comprising wire pairs wound around ferrite cores and arranged to achieve a desired input and output impedance required to impedance match the transmitter to the antenna. However, in high power applications, the ferrite cores become excessively hot and are difficult to cool due to their solid nature. In addition, the windings-based power transformers are typically suitable only for low-bandwidth applications due to excessive windings capacitance. When used in high bandwidth applications, the transformers may require additional expensive tuning and coupling circuits. Use of the tuning and coupling circuits force undesirable design constraints on the associated transmission system.
Hence, a need exists in the art for a high power transformer that has a large operating bandwidth.